4 Answers
4

It can be thousands of light years. In recently launched S06E10 of Star Wars: The Clone Wars (The Lost Missions), Palpatine (who was on Coruscant) choked Count Dooku (who was in his HQ) from thousands of light years away*.

I don't have canon backup, but its possible that force choke could be triggered via communication channel. Or, its just unexplainable for force telekinesis.

*I am still trying to find distance between Coruscant and Raxus Prime. If you know it, please update the answer.

I estimate Raxus to be around 31,000 light years from Coruscant. This is assuming Kiribi is around 5,000 light years away from Coruscant. I measured the ratios of Kibiri and Raxus' distances from Coruscant from the Atlas (which I think is canon?).
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AlizterJan 3 at 19:21

Perhaps it's a line-of-sight thing, even over video screens. "If I can see you, I can choke you."
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Michael Itzoe2 days ago

It seems like the person choking the victim will need to be close to the victim he/she wants to force choke without looking at the victim.

As shown in this example.

'Some individuals were also powerful enough and experienced enough to not require any visuals to kill someone via force choke, such as when Letta Turmond's Jedi backer, later revealed to be Barriss Offee, killed her via a force choke and subsequently framed Ahsoka Tano for the deed.

As well as when Darth Sidious used the ability to kill the Shadow Collective guards standing near the door before opening it to confront his former apprentice, Darth Maul and the latter's apprentice, Savage Oppress.

With visuals it seems they can choke the victim from a long distance away.

ESPECIALLY - Darth Vader was also seen using this ability to express his dissatisfaction with an Imperial officer during one of his Jedi hunts, choking the man while staring pointedly away from him.'

In "Outbound Flight", a (spoilers hidden) "Jedi turned to the Dark Side" chokes his opponent commander who is on his command ship at an unspecified distance - but within visual range for a large battle with multi-minute flight ranges for fighter ships. I believe just before this time they were exchanging bad words over a comlink, and the Jedi held his choking grip for minutes until an unplanned usage of weaponry intended elsewhere had his ship practically destroyed.

can he actually see the commander, or can he only see the ship?
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phantom422 days ago

There was a sudden hiss from the comm. "So," an almost unrecognizable voice ground out. "You think you have won, alien?" The display came alive ......(snip)..... "You were told wrongly," (the fallen Jedi) countered. "The role of the Jedi is to lead and guide, and to destroy all threats." The unburned corner of his lip twisted upward in a bitter smile. And without warning, (Commander)'s head jerked back, his whole body pressing back against his seat. His hand darted to his throat, clutching uselessly at it.
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Jim Klimovyesterday

Users of Force Choke need only to see their victim in order to perform it on them. Per Wookieepedia:

Those among the most experienced with Force Choke needed only a live visual of their victim in order to perform the technique. Darth Vader demonstrated this by choking Admiral Kendal Ozzel over a viewscreen, even though the admiral was on the bridge and Vader was in his meditation chamber. However, this ability requires extreme focus upon the object at hand, any break of concentration and the choke would be removed and the target's freedom of movement restored. Some individuals were also powerful enough and experienced enough to not require any visuals to kill someone via force choke, such as when Letta Turmond's Jedi backer, later revealed to be Barriss Offee, killed her via a force choke and subsequently framed Ahsoka Tano for the deed, as well as when Darth Sidious used the ability to kill the Shadow Collective guards standing near the door before opening it to confront his former apprentice, Darth Maul and the latter's apprentice, Savage Oppress.

Interesting info but doesn't seem to address the distance question. Assume an individual powerful enough to not require a visual - is there still a distance limitation beyond which a victim would be safe ?
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StanDec 2 '13 at 2:17

This is merely regurgitates the info already in the question (Ozzel) and the other 2 examples don't address distance.
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DVKDec 2 '13 at 15:01

This indeed regard to distance. By this statement, we can assume that force choke can be performed as far as a visual communication can be established
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LcSalazarDec 4 '14 at 16:38